Title fixed. Awesome.

Thanks to Pimpernell, I am going to try to clear the P0400 code in our 98 E300 with your above method. I am not confident that the same applies to our model year, but worth a try as I do not (yet) have a code reader of my own.

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85 300D 3 pedal. Current project.
83 300TD (need rear wiper assembly dead or alive)
84 300SD Daily driver
85 300TD almost 400k miles and driven daily.
98 E300D *sold
86 300SDL *sold and made flawless 10 hour journey to new home.